World clock

Nothing is fetched from a server. Your browser takes its own clock, which phones and computers keep synchronised to atomic time, and applies each city's rules from the IANA time zone database, the same data used by operating systems, airlines and calendar apps. When a country changes its rules, the database is updated and the next browser update carries the change.

That also means every card handles daylight saving on its own schedule. North American cities switch on the second Sunday of March and the first Sunday of November, Europe switches on the last Sundays of March and October, and southern-hemisphere cities such as Sydney, Auckland and Santiago do the opposite, moving their clocks forward in spring around September and October. For a few weeks each year the gaps between cities are therefore different from usual.

The small label on each card is the city's offset from Coordinated Universal Time at this moment. Most offsets are whole hours, but India uses UTC+5:30 all year, and a few places use quarter hours, such as Nepal at UTC+5:45. China spans five geographical time zones yet uses a single clock, UTC+8, so sunrise in western China can be after 9:00 AM in winter.

Offsets run from UTC−12 to UTC+14. The extremes are why the same instant can fall on two different calendar dates: when it is Monday morning in Auckland it is still Sunday afternoon in Honolulu. If you need to convert one specific time, for example a meeting at 15:00 in Berlin, the time zone converter shows the result and the date shift directly.

A quick way to find a workable slot is to look at the cities involved and pick the hour where everyone is between 8:00 and 18:00. Europe and India overlap in the European morning; Europe and the US East Coast overlap in the European afternoon; the US West Coast and East Asia only meet early in the morning in California and late in the evening in Tokyo or Seoul. City pages list those hours explicitly for New York, London, Paris, Dubai, Mumbai, Singapore, Tokyo and Sydney.